Structural fasteners of the pin-and-collar type are widely used in highly stressed joinders, such as in the assembly of aircraft. Such fasteners employ a grooved pin and a collar. When the groove in the pin is a thread, the collar is internally threaded in the nature of a nut. When the groove or grooves are in a plane normal to the axis of the pin, the collar usually has an internal cylindrical surface, which is swaged into the groove or grooves. Both types of fastener can be employed with this invention. In many, even most, such installations, when the fastener is installed correctly with the correct residual tension in the pin, it will be sufficiently resistant to vibration without further provisions to resist or prevent removal.
There are other installations where additional features are required to resist loosening or loss of the collar as the consequence of cyclic forces. One well-known example of a fastener which includes such an additional feature is shown in Starr U.S. Pat. No. 3,805,863. This fastener has functioned well for many years in environments where the vibrational forces are very severe, and in which loss of the collar can result in serious risk. For example, in jet engine intake structures the release of the collar into the engine can be dangerous.
As good as it is, the Starr fastener requires a third part, which leads to complications in manufacture and installation. It may also include the penalty of additional weight.
It is an object of this invention to provide a pin and collar fastener which can be installed with conventional tooling, which comprises only the pin and the collar, and which is resistant to very high vibrational forces. When the fastener includes a thread, it is resistant to substantial torque which would tend to loosen the fastener.